Shielding for multi-coil wireless power transfer systems

ABSTRACT

A shield for redirecting magnetic field generated from a plurality of transmitter coils includes a ferromagnetic structure divided into segments by a plurality of boundary regions, each segment comprises a first material having a first magnetic permeability and each boundary region comprises a second material having a second magnetic permeability lower than the first magnetic permeability, where the plurality of boundary regions are configured to resist a propagation of magnetic field from a first area of the ferromagnetic structure to a second area of the ferromagnetic structure, where the first area intercepts the magnetic field generated from at least one active transmitter coil of the plurality of transmitter coils.

BACKGROUND

Electronic devices (e.g., mobile phones, media players, electronicwatches, and the like) operate when there is charge stored in theirbatteries. Some electronic devices include a rechargeable battery thatcan be recharged by coupling the electronic device to a power sourcethrough a physical connection, such as through a charging cord. Using acharging cord to charge a battery in an electronic device, however,requires the electronic device to be physically tethered to a poweroutlet. Additionally, using a charging cord requires the mobile deviceto have a connector (e.g., a receptacle connector) configured to matewith a connector (e.g., a plug connector) of the charging cord. Thereceptacle connector typically includes a cavity in the electronicdevice that provides an avenue within which dust and moisture canintrude and damage the device. Furthermore, a user of the electronicdevice has to physically connect the charging cable to the receptacleconnector in order to charge the battery.

To avoid such shortcomings, wireless charging devices have beendeveloped to wirelessly charge electronic devices without the need for acharging cord. For example, some electronic devices can be recharged bymerely resting on a charging surface of a wireless charging device. Atransmitter coil disposed below the charging surface may produce atime-varying magnetic field that induces a current in a correspondingreceiving coil in the electronic device. The induced current can be usedby the electronic device to charge its internal battery.

Typical wireless charging devices only use a single transmitter coil toperform wireless power transfer. This requires the electronic device tobe placed in a very specific position to effectuate power transfer, suchas directly above the transmitter coil. Some wireless charging devicesuse multiple transmitter coils so that an electronic device can becharged over a broad charging surface area. These types of wirelesscharging devices often have a number of disadvantages. For instance,some wireless charging devices can leak magnetic field into areas of thecharging surface where an electronic device is not positioned. Thisleakage causes heat generation and efficiency losses, which reduce theeffectiveness of the wireless charging device. Furthermore, the leakedmagnetic field can cause unintended interactions with other devices nearor on the charging surface.

SUMMARY

Some embodiments of the disclosure provide shielding structures for amulti-coil wireless charging device that mitigate leakage of magneticfields across its charging surface. In some embodiments, a shield can bedivided into segments by boundary regions. The boundary regions caninclude material having a magnetic permeability that is lower than amagnetic permeability of the segments so that magnetic fieldspropagating through the shield will encounter resistance from theboundary regions. Resistance from the boundary regions reduce leakage ofmagnetic field across the charging surface, thereby minimizing powerlosses and enhancing power transfer efficiency.

In some embodiments, a wireless charging system includes a shield forredirecting magnetic field generated from a plurality of transmittercoils, the shield including a ferromagnetic structure divided intosegments by a plurality of boundary regions, each segment comprises afirst material having a first magnetic permeability and each boundaryregion comprises a second material having a second magnetic permeabilitylower than the first magnetic permeability, wherein the plurality ofboundary regions are configured to resist a propagation of magneticfield from a first area of the ferromagnetic structure to a second areaof the ferromagnetic structure, wherein the first area intercepts themagnetic field generated from at least one active transmitter coil ofthe plurality of transmitter coils.

The plurality of boundary regions can extend across the entire shieldfrom edge to edge. The plurality of boundary regions can intersect oneanother at a plurality of points. The plurality of points can align withcenters of respective transmitter coils. The plurality of boundaryregions can include a continuous strip of the second material. Theplurality of boundary regions can include a non-continuous strip of thesecond material. In certain embodiments, the second material includes adielectric material. In further embodiments, the second materialcomprises a conductive material. In some embodiments, the secondmaterial comprises air. The first area can include a first portion ofsegments, and the second area can include a second portion of segments.The first area can be a charging area that corresponds to an area of theshield that overlaps the at least one active transmitter coil, and thesecond area can be a leakage area that overlaps at least one inactivetransmitter coil of the plurality of transmitter coils.

In some embodiments, a wireless power transmitting device to transmitmagnetic field for wireless power transfer can include a housing havinga charging surface, a plurality of transmitter coils disposed within thehousing below the charging surface and configured to generate magneticfield during a charging event, and a shield comprising a ferromagneticstructure to redirect at least a portion of the magnetic field generatedby the plurality of transmitter coils during the charging event, wherethe ferromagnetic structure is divided into segments by a plurality ofboundary regions, each segment comprises a first material having a firstmagnetic permeability and each boundary region comprises a secondmaterial having a second magnetic permeability lower than the firstmagnetic permeability.

Each boundary region can be tangent to at least one of the transmittercoils and can bisect at least one other of the transmitter coils. Thewireless power transmitting device can further include a driver boarddisposed below the plurality of transmitter coils. The shield can bedisposed between the plurality of transmitter coils and the driver boardso that the magnetic field is prevented from exposing on componentsmounted on the driver board. The shield can include a top side and abottom side so that the magnetic field enters and exits the shield intoand out of the top side. The plurality of boundary regions can beconfigured to resist a propagation of magnetic field from a first areaof the shield to a second area of the shield. The plurality of boundaryregions can intersect one another at a plurality of points, where theplurality of points can align with centers of respective transmittercoils. The first area can intercept the magnetic field generated from atleast one active transmitter coil of the plurality of transmitter coils.The second material can include a dielectric material.

A better understanding of the nature and advantages of embodiments ofthe present invention may be gained with reference to the followingdetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating a wireless charging deviceconfigured to perform wireless power transfer.

FIG. 2 is a simplified diagram illustrating an exemplary transmittercoil arrangement within a wireless charging device.

FIG. 3A is a simplified diagram illustrating a simplifiedcross-sectional view of an electronic device resting on a wirelesscharging device and the electrical interactions between them duringwireless power transfer.

FIG. 3B is a simplified diagram illustrating a simplified top-down viewof FIG. 3A.

FIG. 4A is a simplified diagram illustrating a simplifiedcross-sectional view of an electronic device resting on a wirelesscharging device with a segmented shield and the electrical interactionsbetween them during wireless power transfer, according to someembodiments of the present disclosure.

FIG. 4B is a simplified diagram illustrating a simplified top-down viewof FIG. 4A, according to some embodiments of the present disclosure.

FIG. 5A is a simplified diagram illustrating an exemplary segmentedshield having a plurality of boundary regions in a first configurationthat divide the segmented shield into segments, according to someembodiments of the present disclosure.

FIG. 5B is a simplified diagram illustrating an exemplary segmentedshield having a plurality of boundary regions in a second configurationthat divide the segmented shield into segments, according to someembodiments of the present disclosure

FIG. 6A is a simplified diagram illustrating a multi-coil arraysuperimposed over the segmented shield shown in FIG. 5B, according tosome embodiments of the present disclosure.

FIG. 6B is a simplified diagram illustrating a zoomed-in top-down viewof transmitter coils in the multi-coil array of FIG. 6A superimposedover the segmented shield shown in FIG. 5B, according to someembodiments of the present disclosure

FIG. 7A is a simplified diagram illustrating an exemplary segmentedshield that has boundary regions that are configured with bridgingstructures between segments, according to some embodiments of thepresent disclosure.

FIG. 7B is a simplified diagram illustrating an exemplary segmentedshield having an outer profile that corresponds to the outer profile ofa multi-coil array configured in the transmitter coil arrangement shownin FIG. 2, according to some embodiments of the present disclosure

FIG. 8 is a simplified diagram illustrating a simplified, exploded viewof an exemplary wireless charging device having a segmented shield,according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the disclosure describe a shield for a multi-coilwireless charging device that mitigates leakage of magnetic fieldsacross its charging surface. The shield can be housed in an enclosurealong with multiple transmitter coils, which are configured to generatetime-varying magnetic fields capable of inducing current in a receiverof an electronic device or of a docking station with which theelectronic device is coupled. The transmitter coils can be arranged in amanner that enables the multi-coil wireless charging device to providepower to the electronic device positioned anywhere within a broadcharging surface. For instance, when the electronic device is placed ononly a portion of the charging surface, magnetic fields from thewireless charging device can be confined to areas of the chargingsurface immediately surrounding the electronic device without leaking toother areas of the charging surface where the electronic device is notpositioned. According to embodiments, the shield substantially reducesthe leakage of magnetic fields across the charging surface, therebyresulting in improved power transfer efficiency and reduced powerlosses. Aspects of multi-coil wireless charging devices and shields arediscussed in detail further herein.

I. Multi-Coil Wireless Charging Device

FIG. 1 illustrates a wireless charging device 100 configured to performwireless power transfer. Wireless charging device 100 can include acharging surface 102 upon which an electronic device 106 having awireless power receiver can be placed to wirelessly charge its battery.In some embodiments, charging surface 102 may be a region of a topsurface 104 of wireless charging device 100 that spans across a vastmajority, if not the entire area, of top surface 104. Time-varyingmagnetic fields generated by wireless charging device 100 can propagatethrough regions of top surface 104 within charging surface 102 and forma continuous region within which devices can wirelessly receive power.Time-varying magnetic fields can be generated by multiple transmittercoils embedded within wireless charging device 100. For instance,wireless charging device 100 can include a transmitter coil arrangementas shown in FIG. 2.

FIG. 2 illustrates an exemplary transmitter coil arrangement 200 withinwireless charging device 100. The illustration of FIG. 2 shows wirelesscharging device 100 with top surface 104 removed so that the embeddedtransmitter coil arrangement 200 may be seen. Transmitter coilarrangement 200 can include multiple arrays of transmitter coilsarranged in different layers and in a non-concentric fashion so thatwhen all of the transmitter coils are operating, an array of magneticfields can be generated across charging surface 102.

Electronic device 106 can be any suitable device configured to receivepower from wireless charging device 100. For example, electronic device106 can be a portable electronic device (e.g., a mobile phone, a mediaplayer, an electronic watch, and the like), a docking station, or anaccessory electronic device, each having a receiver coil configured toreceive power when exposed to magnetic fields produced by wirelesscharging device 100. When electronic device 106 in FIG. 1, is placed oncharging surface 102 of wireless charging device 100, time-varyingmagnetic fields generated by the transmitter coils can induce acorresponding current in a receiver coil of device 106, as shown in FIG.3A.

FIG. 3A illustrates a simplified cross-sectional view of electronicdevice 106 resting on wireless charging device 100 and the electricalinteractions between receiver coil 302 and a transmitter coil 300-1during wireless power transfer. Transmitter coil 300-1 can be onetransmitter coil of a plurality of transmitter coils, such as N numberof transmitter coils where transmitter coil 300-N is the N^(th)transmitter coil. Transmitter coils 300-1 to 300-N can be organized astransmitter coil arrangement 200 shown in FIG. 2.

During wireless power transfer, transmitter coil 300-1 can generatetime-varying magnetic field 304, which can propagate through both devicehousings and be received by receiver coil 302. Time-varying magneticfield 304 interacts with receiver coil 302 to generate a correspondingcurrent in receiver coil 302. The generated current can be used tocharge a battery for operating electronic device 106.

Although magnetic field 304 can flow towards receiver coil 302, magneticfield 304 can also flow towards other components, e.g., components 308,310, 312, and 314, within wireless charging device 100, such as controlmicroprocessors, power electronics, and the like. Exposing components308, 310, 312, and 314 to magnetic field 304 can disturb and compromisethe performance of those components. Thus, a shield 306 can beimplemented between transmitter coils 300-1 through 300-N and components308, 310, 312, and 314, as shown in FIG. 3A. Shield 306 can be formed ofa material that has a high magnetic permeability, such as ferrite.Shield 306 can thus redirect magnetic field 304 to prevent exposure uponcomponents 308, 310, 312, and 314. Redirection of magnetic field 304occurs because of the high magnetic permeability of shield 306 whencompared to air. Accordingly, magnetic field 304 may prefer to flow intoshield 306 instead of flowing out of it. In some instances, magneticfield 304 flows into and out of a first side of shield 306 (i.e., thetop side of shield 306 as shown in FIG. 3A) instead of flowing throughit and exiting out of a second side of shield 306 (i.e., the bottom sideof shield 306 as shown in FIG. 3A). Thus, components 308, 310, 312, and314 receive minimal, if any, exposure to magnetic field 304.

Typical shields, such as shield 306 in FIG. 3A, are structures formed ofa continuous piece of ferromagnetic material. The continuousconstruction of shield 306 means that its structure is formed offerromagnetic material throughout its entire build, without any regionsof non-ferromagnetic material. For instance, portions of the shield thatdirectly overlap transmitter coils are continuous in construction and donot have regions of non-ferromagnetic material. While this constructioneffectively shields the magnetic field, its continuous structure alsoallows magnetic field to propagate across itself and leak out in areaswhere an electronic device is not positioned. For instance, as shown inFIG. 3A, leaking magnetic field 307 can propagate along shield 306 allthe way to an area of shield 306 where electronic device 106 is notpositioned. Another perspective of the leakage area is shown in FIG. 3B.

FIG. 3B illustrates a top-down view of magnetic field leakage whenelectronic device 106 is positioned on wireless charging device 100 forwireless power transfer. Electronic device 106 can receive power fromwireless charging device 100 by merely resting on charging surface 102of wireless charging device 100. During wireless power transfer,magnetic field 304 is generated by transmitter coil 300-1 and receivedby receiver coil 302 in electronic device 106, as discussed herein withrespect to FIG. 3A. Magnetic field 304 may propagate around theimmediate areas surrounding electronic device 106, which is shown ascharging area 320. Charging area 320 can also be defined by an area ofshield 306 that intercepts magnetic field generated by transmitter coil300-1. However, given the continuous construction of shield 306,magnetic field 307 can propagate along a length of shield 306 and leakto areas where electronic device 106 is not positioned, such as leakagearea 322. It is to be appreciated that charging area 320 and leakagearea 322 correspond to areas of shield 306 as well as wireless chargingdevice 100 because a substantial portion of their structurescorrespond/overlap with each other. Thus, charging area 320 and leakagearea 322 are not specific to either shield 306 or wireless chargingdevice 100, but apply to both shield 306 and wireless charging device100.

This leaked magnetic field can dissipate energy in the form of heat,thereby decreasing the power transfer efficiency of wireless chargingdevice 100. Furthermore, the leaked magnetic field can disturb otherelectronic devices that are placed on charging surface 102 but notintended and/or not configured to receive charge from wireless chargingdevice 100. This unintended interaction with the leaked magnetic fieldcan damage components in the other electronic devices, such as a radiofrequency chip.

Thus, according to some embodiments of the present disclosure, asegmented shield structure is designed to mitigate leakage of magneticfield to areas of the shield where magnetic field is not needed orintended to exist. As will be discussed in more detail further herein,the segmented shield has boundary regions of low permeability that canconfine magnetic fields to a charging area, e.g., charging area 320,where an electronic device is receiving charge, and mitigate leakage ofmagnetic field to areas outside of the charging area, e.g., leakage area322.

II. Wireless Charging Device With Shielding

Embodiments of the disclosure describe a wireless charging device thathas a segmented shield for mitigating leakage of magnetic field acrossits charging surface. The segmented shield can be formed of aferromagnetic structure that includes regions of low magneticpermeability. These regions can hinder the propagation of magnetic fieldacross the shield to mitigate leakage of the magnetic field to areasoutside of a charging area.

FIG. 4A illustrates a simplified cross-sectional view of electronicdevice 106 resting on a wireless charging device 400 that includes asegmented shield 406. Wireless charging device 400 is substantiallysimilar to wireless charging device 100 in FIG. 3A, but different inthat wireless charging device 400 includes segmented shield 406 that hasboundary regions of low magnetic permeability, according to embodimentsof the present disclosure. Thus, the other components shared betweenwireless charging device 100 and 400 will not be discussed here, andthat such details can be referenced in the discussion with respect toFIG. 3A.

During wireless power transfer, transmitter coil 400-1 can generatetime-varying magnetic field 404, which can propagate through both devicehousings and be received by receiver coil 302. Time-varying magneticfield 404 interacts with receiver coil 302 to generate a correspondingcurrent in receiver coil 302. The generated current can be used tocharge a battery for operating electronic device 106.

As aforementioned herein, segmented shield 406 can be implementedbetween transmitter coils 400-1 through 400-N and components 408, 410,412, and 414, as shown in FIG. 4A, to redirect magnetic field 404 toprevent exposure upon components 408, 410, 412, and 414. Redirection ofmagnetic field 404 occurs because of the high magnetic permeability ofsegmented shield 406 when compared to air. Accordingly, magnetic field404 may prefer to flow into segmented shield 406 instead of flowing outof it. In some instances, magnetic field 404 flows into and out of afirst side of segmented shield 406 (i.e., the top side of segmentedshield 406 as shown in FIG. 4A) instead of flowing through it andexiting out of a second side of segmented shield 406 (i.e., the bottomside of segmented shield 406 as shown in FIG. 4A). Thus, components 408,410, 412, and 414 receive minimal, if any, exposure to magnetic field404.

According to some embodiments of the present disclosure, unlike shield306 in FIG. 3A, segmented shield 406 can be a structure that is dividedinto segments by a plurality of boundary regions. For instance,segmented shield 406 can include a boundary region 404 that dividessegmented shield 406 into segments 416 and 418. Boundary region 404 canbe configured to have low magnetic permeability which allows it toresist and/or obstruct the propagation of magnetic field through certainareas of segmented shield 406. Thus, boundary region 404 cansubstantially confine magnetic fields generated during wireless powertransfer to certain areas of segmented shield 406 and wireless chargingdevice 400. As an example, confined magnetic field 407 can be confinedby boundary region 404 so that magnetic field 407 exits out of segmentedshield 406 at or near boundary region 404 before it can propagate acrossthe entire segmented shield 406. By resisting and/or obstructing thepropagation of magnetic field across segmented shield 406, magneticfields generated during wireless power transfer can be confined to areasof segmented shield 406 and wireless charging device 400 thatimmediately surround electronic device 106, thereby minimizing leakageof magnetic fields and enhancing power efficiency.

Another perspective of this concept is shown in FIG. 4B, whichillustrates a top-down view of FIG. 4A. By incorporating boundary region404, magnetic field can be substantially confined to charging area 320,and substantially resisted from leaking to areas outside of chargingarea 320. For instance, boundary region 404 can confine magnetic fieldsto propagate within only segment 416 and substantially resistpropagation of the magnetic fields to segment 418. Accordingly,segmented shield 406 can mitigate leakage of magnetic field such that aleakage area (e.g., leakage area 322 in FIG. 3B) is not created duringwireless power transfer.

As shown in FIG. 4B, boundary region 404 can have a length that isgreater than its width so that boundary region 404 has an elongatedprofile. In some embodiments, boundary region 404 has a length that is amultitude times greater than its width so that boundary region 404 has abuild similar to a stripe. Boundary region 404 can extend across atleast a portion of segmented shield 406. For instance, boundary region404 can extend across segmented shield 406 from edge to edge.Furthermore, even though boundary region 404 is shown as a straightline, embodiments are not so limited. Boundary regions in otherembodiments can be curved or angled, or be configured to form a polygon.Additionally, boundary regions in other embodiments can be formed of aperforated line so that when viewed generally, boundary region iselongated like a stripe, but when viewed narrowly, boundary region isformed of a plurality of small dots or non-elongated regions of lowmagnetic permeability that are arranged in a line.

Boundary region 404 can be configured to have a magnetic permeabilitythat is lower than the magnetic permeability of segments 416 and 418.For instance, boundary region 404 can be an air gap. In such instances,each segment 416 and 418 can be individually fixed in position, such aswith an adhesive or with one or more bridging structures that attachneighboring segments with one another, as will be discussed furtherherein.

In some additional and alternative embodiments, boundary region 404 canbe formed of a diamagnetic material that has non-conductive propertiesand structural rigidity, unlike an air gap. For instance, boundaryregion 404 can be formed of a dielectric material that has a highdielectric breakdown voltage such as epoxy resin,polytetrafluoroethylene (PTFE), high density polyethylene (HDPE), andthe like. The type of material used to form boundary region 404 can alsohave properties that minimize interference during device operation, suchas materials with low radio frequency (RF) loss (which include thematerials listed herein). By using a material that has structuralrigidity, segmented shield 400 can have a structural composition like asolid continuous shield structure, but have electrical propertiesreflective of a segmented structure.

Furthermore, boundary region 404 can be formed of a diamagnetic materialthat has conductive properties. As an example, boundary region 404 canbe formed of copper, or any other conductive material that has arelative permeability of at least −1.0.

A. Boundary Region Configurations

Although FIGS. 4A and 4B illustrate segmented shield 406 as having onlyone boundary region, segmented shield 406 can include a plurality ofboundary regions, according to some embodiments of the presentdisclosure. For instance, FIG. 5A illustrates an exemplary segmentedshield 500 having a plurality of boundary regions 502 a-d that dividesegmented shield 500 into segments 506 a-h. Boundary regions 502 a-c canbe vertically oriented, and boundary region 502 d can be horizontallyoriented to divide segmented shield 500 into a plurality of rectangularsegments 506 a-h. During wireless power transfer, boundary regions 502a-d can substantially mitigate propagation of magnetic field acrosssegmented shield 500, and thus help confine magnetic field to certainareas of segmented shield 500. In some embodiments, magnetic field canbe substantially confined within segment 506 b, or the magnetic fieldcan be confined within segments 506 b and 506 c if active transmittercoil(s) are overlapped by both segments 506 b and 506 c such that thetransmitter coil(s) emit magnetic field in segments 506 b and 506 c.Although boundary regions 502 a-d are shown as solid lines, it is to beappreciated that boundary regions 502 a-d have a width dimension.

The degree at which boundary regions 502 a-d resist the propagation ofmagnetic fields across its region can vary depending on their widths.Wider boundary regions have larger effective resistances againstpropagation of magnetic field. Conversely, narrower boundary regionshave smaller resistances. However, adjusting the width can affect thetotal inductance of the multi-coil array. For instance, wider boundaryregions decrease the total inductance, while narrower boundary regionsincrease the total inductance. Thus, the width of boundary regions 502a-d can be tuned specifically to the amount of resistance and inductancedesired. In some embodiments, the width of boundary regions 502 a-d canrange between 1 and 5 mm.

The configuration shown in FIG. 5A is merely exemplary and not intendedto be limiting. That is, other embodiments can have more or lessboundary regions that divide a segmented shield into more or less thanthe number shown in FIG. 5A. Furthermore, boundary regions do not haveto be oriented in strictly vertical and horizontal orientations; rather,boundary regions can be oriented in any configuration. For example, FIG.5B illustrates an exemplary segmented shield 501 divided into segments512 by boundary regions 510 that include diagonally oriented boundaryregions. Letter designations are not assigned in FIG. 5B for claritypurposes given the large number of boundary regions and segments.Boundary regions 510 can include diagonal and horizontal boundaryregions that form triangular segments 512. In some embodiments, eachboundary region can extend across the entire segmented shield 501 fromedge to edge. It is to be appreciated that the configuration of boundaryregions, segments, and boundary region orientations can vary by design.For instance, the configuration can be designed according to an array oftransmitter coils positioned adjacent to the segmented shield. As anexample, boundary regions 510 can be configured according to amulti-coil array of transmitter coils, as will be discussed in furtherdetail herein.

FIG. 6A illustrates a multi-coil array 600 superimposed over segmentedshield 501, according to some embodiments of the present disclosure.Multi-coil array 600 can be arranged to maximize a charging surface of awireless charging device, as discussed herein with respect to FIG. 2.Boundary regions 510 can be positioned to confine magnetic fieldsgenerated by one or more transmitter coils so that if some transmittercoils are activated in only one area of the wireless charging device,magnetic fields do not substantially leak across to other areas of thecharging surface, as discussed herein with respect to FIGS. 4A and 4B.The configuration of the boundary regions are discussed in furtherdetail in FIG. 6B.

FIG. 6B illustrates a zoomed-in top-down view of transmitter coils 602a-d in multi-coil array 600 superimposed over segmented shield 501having boundary regions 510 that include boundary regions 604 a-l,according to some embodiments of the present disclosure. Othertransmitter coils are faded and drawn with dotted lines to indicatetheir location without detracting from the focus on transmitter coils602 a-d and boundary regions 604 a-l, which are drawn with solid lines.

As shown in FIG. 6B, boundary regions 604 a-l can be arranged so thateach boundary region is positioned tangential to at least onetransmitter coil while also positioned through the center of at leastone other transmitter coil. For instance, boundary region 604 c ispositioned tangential to transmitter coils 602 b and 602 d while alsopositioned through the center of transmitter coils 602 a and 602 c. Allboundary regions of a segmented shield can be arranged in this manner sothat as a whole, each transmitter coil is bisected by one or moreboundary regions and has one or more other boundary regions that aretangential to it. As an example, transmitter coil 602 a is bisected byboundary regions 604 c, 604 f, and 604 j, and has boundary regions 604i, 604 d, 604 g, 604 k, 604 b, and 604 e (recited in a clockwisefashion) that are positioned tangential to it. The nature of thisconfiguration results in a segmented shield design where bisectingboundary regions intersect at the center of each transmitter coil, andtangential boundary regions are positioned around each transmitter coiland effectively form a perimeter around each transmitter coil.

This arrangement is designed to maximize resistance against propagationof magnetic field between transmitter coils (i.e., mitigate leakage),but minimize interference with the magnetic field generated within eachtransmitter coil (i.e., maximize inductance of the transmitter coils).As mentioned herein, bisecting boundary regions intersect at the centerof a transmitter coil. Given that an active transmitter coil generates amagnetic field that emanates radially to/from the center of the activetransmitter coil, bisecting boundary regions are positioned parallel tothe propagation of generated magnetic fields. Accordingly, bisectingmagnetic fields do not significantly interfere with the generatedmagnetic fields. On the other hand, tangential boundary regions arepositioned substantially perpendicular to the radial direction ofgenerated magnetic fields. Thus, tangential boundary regions cansubstantially interfere and resist the propagation of magnetic fieldacross the tangential boundary regions. As a result, the tangentialboundary regions can effectively form a perimeter of low magneticpermeability to confine the generated magnetic field to areasimmediately surrounding the active transmitter coil, thereby forming acharging area over the active transmitter coil. For instance, ifcontinuing with the example with respect to transmitter coil 602 a,bisecting boundary regions 604 c, 604 f, and 604 j are positionedparallel to magnetic field generated by transmitter coil 602 a, andtangential boundary regions 604 i, 604 d, 604 g, 604 k, 604 b, and 604 eare positioned perpendicular to the magnetic field generated bytransmitter coil 602 a. The charging area is then defined as a hexagonalshape formed by the tangential boundary regions surrounding transmittercoil 602 a.

A charging area is not limited to the area over one transmitter coil;rather, the size and shape of the charging area is defined by the numberand arrangement of active transmitter coils. Larger groups of activetransmitter coils result in a larger charging areas that correspond tothe size and shape of the arrangement of the active transmitter coils.For instance, if transmitter coils 602 a and 602 b are active, then thecharging area can be defined by boundary regions 604 i, 604 d, 604 g,604 l, 604 a, and 604 e (recited in clockwise order). Thus, whentransmitter coils 602 a and 602 b are active during wireless powertransfer, magnetic fields generated by transmitter coils 602 a and 602 bcan be substantially confined within that charging area, and magneticfield can be substantially prevented from leaking out of that chargingarea, thereby avoiding excessive heating from leaked magnetic fields andresulting in a loss of power efficiency.

It is to be appreciated that the image shown in FIG. 6B showstransmitter coils superimposed over boundary regions 604 a-l. Thus,descriptions regarding intersection and the like are not intended tomean that the boundary regions and the transmitter coils are actually inphysical contact with one another. Rather, the discussion pertains totheir position relative to one another. One skilled in the artunderstands that the transmitter coils and the boundary regions of thesegmented shield are positioned in separate layers of a wirelesscharging device. Furthermore, although not specifically labeled forclarity purposes, segments of shield 500 are understood to be the areasdelineated by boundary regions 604 a-l. For instance, segments of shield500 in FIG. 6B have a triangular shape and are oriented such that sixtriangular segments are positioned over each transmitter coil.

As shown in FIGS. 4B, 5A-B, and 6A-B, boundary regions can be configuredto have low magnetic permeability continuously across its entire length.However, such embodiments are not intended to be limiting, and thatother embodiments can have boundary regions that do not have lowmagnetic permeability continuously across its entire length. Forinstance, forming a boundary region with an air gap can result in asegment that is freely movable unless it is fixed to a static structure.Thus, in some embodiments, segments can be fixed in place by configuringthe boundary regions with one or more bridging structures as shown inFIG. 7A.

FIG. 7A illustrates an exemplary segmented shield 700 that has boundaryregions 702 that are configured with bridging structures 704 betweensegments 706, according to some embodiments of the present disclosure.These bridging structures can be extensions of segments 706 that bridgewith neighboring segments to connect them together. Since bridgingstructures 704 are extensions of segments 706, bridging structures 704can be formed of the material as segments 706, which is formed of amaterial having high magnetic permeability. Accordingly, instead ofbeing a continuous strip, boundary regions 702 can be a dashed stripthat includes sections of low magnetic permeability and high magneticpermeability. It is to be appreciated that boundary regions 702 do nothave to include air as the low magnetic permeability component. Rather,the dashed strip configuration can apply to other types of boundaryregions, such as boundary regions formed with a dielectric material or aconductive material discussed herein.

As shown in FIGS. 3B, 4B, 5A-B, 6A, and 7A, the outer profile of asegmented shield can correspond to the outer profile of a wirelesscharging device; however, embodiments are not so limited. As an example,some embodiment can have outer borders that follow the profile of amulti-coil array, as shown in FIG. 7B, which illustrates an exemplarysegmented shield 701 having an outer profile that corresponds to theouter profile of a multi-coil array configured in the transmitter coilarrangement discussed herein with respect to FIG. 2, according to someembodiments of the present disclosure. Forming a segmented shield thisway can reduce the amount of ferrite needed to manufacture segmentedshield 701. Reducing the amount of ferrite used to form the shield cansave cost.

III. Wireless Charging Device With Segmented Shielding

FIG. 8 illustrates a simplified, exploded view of an exemplary wirelesscharging device 800 having a segmented shield 812, according to someembodiments of the present disclosure. Wireless charging device 800 caninclude a housing formed of two shells: a first shell 802 and a secondshell 804. First shell 802 can mate with second shell 804 to form aninterior cavity within which internal components may be positioned.First and second shells 802 and 804 can also include notches 806 a and806 b, respectively, that form an opening within the housing when firstand second shells 802 and 804 are mated. An electrical connector 808,such as a receptacle connector, can be positioned within the opening sothat wireless charging device 800 can receive power from an externalpower source through a cable connected to electrical connector 808. Insome embodiments, electrical connector 808 may include a plurality ofcontact pins and a plurality of terminals electrically coupled to thecontact pins so that power can be routed from the external power sourceto driver board 810 to provide power for wireless power transfer.

The interior cavity formed between mated first and second shells 802 and804 can include components that generate the magnetic field forperforming the wireless charging of an electronic device. As an example,an array of transmitter coils 810 can be housed within the inner cavity.Transmitter coils 810 can be operated to generate time-varying magneticfields that propagate above the top surface of top shell 802 duringwireless power transfer. The arrangement of transmitter coils 810 canform a charging surface 816 on to shell 802 within which an electronicdevice can be placed to receive power from wireless charging device 800.The electronic device can be placed in any area of the charging surfaceto receive power.

In addition to transmitter coils 810, wireless charging device 800 canalso include a segmented shield 812 according to some embodiments of thepresent disclosure. Segmented shield 812 can be configured to preventexposure of magnetic field upon electrical components within wirelesscharging device 800 and mitigate leakage of magnetic field across itstructure, as discussed herein with respect to FIGS. 4A-B. Accordingly,segmented shield 812 can be positioned within wireless charging device800 in a suitable location for blocking magnetic field from exposing oncomponents within wireless charging device 800. For example, segmentedshield 812 can be positioned between transmitter coils 810 and a driverboard 814 that houses the components within wireless charging device800.

Implementing segmented shield 812 prevents magnetic field from exposingon sensitive electronic components with wireless charging device 800 andmitigates leakage of magnetic field across charging surface 816 to areaswhere no electronic device is positioned on charging surface 816.Preventing leakage of magnetic fields can minimize unnecessary deviceheating and power losses, thereby enhancing power transfer efficiency.

Although the invention has been described with respect to specificembodiments, it will be appreciated that the invention is intended tocover all modifications and equivalents within the scope of thefollowing claims.

What is claimed is:
 1. A shield for redirecting magnetic field generatedfrom a plurality of transmitter coils, the shield comprising: aferromagnetic structure divided into segments by a plurality of boundaryregions, each segment comprises a first material having a first magneticpermeability and each boundary region comprises a second material havinga second magnetic permeability lower than the first magneticpermeability, wherein the plurality of boundary regions comprises: afirst subset of boundary regions forming a border around at least aportion of a transmitter coil of the plurality of transmitter coils, thefirst subset is configured to resist a propagation of magnetic fieldfrom a first area within the border to a second area outside of theborder, wherein the first area intercepts the magnetic field generatedfrom the transmitter coil; and a second subset of boundary regionsintersecting at a center of the transmitter coil.
 2. The shield of claim1, wherein the plurality of boundary regions extend across the entireshield from edge to edge.
 3. The shield of claim 1, wherein theplurality of boundary regions intersect one another at a plurality ofpoints.
 4. The shield of claim 3, wherein the plurality of points alignwith centers of respective transmitter coils.
 5. The shield of claim 1,wherein the plurality of boundary regions comprise a continuous strip ofthe second material.
 6. The shield of claim 1, wherein the plurality ofboundary regions comprise a non-continuous strip of the second material.7. The shield of claim 1, wherein the second material comprises adielectric material.
 8. The shield of claim 1, wherein the secondmaterial comprises a conductive material.
 9. The shield of claim 1,wherein the second material comprises air.
 10. The shield of claim 1,wherein the first area includes a first portion of segments, and thesecond area includes a second portion of segments.
 11. The shield ofclaim 10, wherein the first area is a charging area that corresponds toan area of the shield that overlaps the at least one active transmittercoil, and the second area is a leakage area that overlaps at least oneinactive transmitter coil of the plurality of transmitter coils.
 12. Awireless power transmitting device to transmit magnetic field forwireless power transfer, the wireless power transmitting devicecomprising: a housing having a charging surface; a plurality oftransmitter coils disposed within the housing below the charging surfaceand configured to generate magnetic field during a charging event; and ashield comprising a ferromagnetic structure to redirect at least aportion of the magnetic field generated by the plurality of transmittercoils during the charging event, wherein the ferromagnetic structure isdivided into segments by a plurality of boundary regions, each segmentcomprises a first material having a first magnetic permeability and eachboundary region comprises a second material having a second magneticpermeability lower than the first magnetic permeability, and wherein theplurality of boundary regions comprises: a first subset of boundaryregions forming a border around at least a portion of a transmitter coilof the plurality of transmitter coils, the first subset is configured toresist a propagation of magnetic field from a first area within theborder to a second area outside of the border, wherein the first areaintercepts the magnetic field generated from the transmitter coil; and asecond subset of boundary regions intersecting at a center of thetransmitter coil.
 13. The wireless power transmitting device of claim12, wherein each boundary region is tangent to at least one of thetransmitter coils and bisects at least one other of the transmittercoils.
 14. The wireless power transmitting device of claim 12, furthercomprising a driver board disposed below the plurality of transmittercoils.
 15. The wireless power transmitting device of claim 14, whereinthe shield is disposed between the plurality of transmitter coils andthe driver board so that the magnetic field is prevented from exposingon components mounted on the driver board.
 16. The wireless powertransmitting device of claim 15, wherein the shield comprises a top sideand a bottom side so that the magnetic field enters and exits the shieldinto and out of the top side.
 17. The wireless power transmitting deviceof claim 12, wherein the plurality of boundary regions intersect oneanother at a plurality of points.
 18. The wireless power transmittingdevice of claim 12, wherein the first area intercepts the magnetic fieldgenerated from at least one active transmitter coil of the plurality oftransmitter coils.
 19. The wireless power transmitting device of claim12, wherein the second material comprises a dielectric material.